Monitoring location Potomac River Near Wash, DC Little Falls Pump Sta - USGS-01646500

LOCATION.-- On left bank just upstream from Little Falls Dam, 1 mi upstream from District of Columbia boundary line, 1.2 mi upstream from Chain Bridge, 1.8 mi east of Langley, Fairfax County, and at mile 117.4. PERIOD OF RECORD.-- March 1930 to current year. GAGE.--Water-stage recorder, crest-stage gage, and concrete control. Datum of gage is 37.04 ft above North American Vertical Datum of 1988. Prior to June 7, 1930, nonrecording gage, and June 7, 1930 to Jan. 22, 1965, water-stage recorder at site 1 mi upstream on right bank at same gage datum. REMARKS.--Diversions since June 1959. For unregulated statistics of monthly mean data and summary statistics for water years 1930 to 1958, reference WDR MD-DE-DC-02-1. Diversions at Great Falls through aqueducts since June 1959, from gage pool at Little Falls Dam; since October 1958, at Rockville Filtration Plant; since April 1961, at Potomac Filtration Plant; since October 1961, at Fairfax Water Treatment Plant (from Goose Creek); since April 1964, at Violets Lock to Chesapeake and Ohio Canal; and since October 1985, at Fairfax County Water Authority Treatment Plant. Low flow affected slightly prior to July 1981 by Stony River Reservoir, since December 1950, by Savage River Reservoir (see station 01597500), and since July 1981, by Jennings Randolph Lake. EXTREMES OUTSIDE PERIOD OF RECORD.-- Flood of June 2, 1889, was of approximately the same magnitude as that of March 19, 1936. PERIOD OF DAILY RECORD (Water Quality).-- SPECIFIC CONDUCTANCE: October 1988 to current year. WATER TEMPERATURE 7.1 ft from riverbed (top): October 1988 to September 2019. WATER TEMPERATURE 4.1 ft from riverbed (middle): July 2006 to September 2019. WATER TEMPERATURE 1.0 ft from riverbed (bottom): July 2006 to September 2019. NITRATE PLUS NITRITE IN SITU (BURST data collection): December 2011 to current year. NITRATE PLUS NITRITE IN SITU (SDI-12 data collection): July 2019 to current year. SPECIFIC CONDUCTANCE, MULTIPARAMETER SONDE: November 2013 to current year. TEMPERATURE, MULTIPARAMETER SONDE: November 2013 to current year. pH: November 2013 to current year. DISSOLVED OXYGEN: November 2013 to current year. TURBIDITY: November 2013 to current year. REMARKS (Water Quality).-- Turbidity values greater than 1,000 formazin nepthelometric units (FNU) exceed the instrument calibration range. Values above 1,000 FNU are included in the record but are presumed to have lower accuracy. The accuracy limit of the turbidity sensor in low turbidity water is +/- 0.3 FNU. October 1, 2024: dValues are censored and qualified as Less Than 0.3 FNU if they are recorded below 0.3 FNU.